Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$157.63	6.550%	$167.9548	$167.95	$167.95	$168.00
Purchase #2	$6.89	3.740%	$7.1477	$7.15	$7.15	$7.10
Purchase #3	$42.40	6.220%	$45.0373	$45.04	$45.05	$45.00
Purchase #4	$216.47	3.414%	$223.8603	$223.86	$223.85	$223.90
Purchase #5	$213.96	12.250%	$240.1701	$240.17	$240.15	$240.20
Purchase #6	$11.37	10.137%	$12.5226	$12.52	$12.50	$12.50
Purchase #7	$36.69	10.137%	$40.4093	$40.41	$40.40	$40.40
7 purchase totals =	$685.41		$737.1021	$737.10	$737.05	$737.10